Today, almost every electronic application provides a user interface for human-machine interactions, such as a push button, a keypad, and a mouse. Among various user interface related technologies, touch-sensitive displays (also known as “touch screen” or “touch panel”) are becoming more and more popular for being intuitive and user-friendly. Touch-sensitive displays are widely used in electronic applications, in particular, portable devices and public systems. As a user interface, a touch-sensitive display detects a user contact with the display, translates the user contact into an electronic signal, and transmits the signal to a signal processor. Through signal analysis, the signal processor determines the location of the user contact on the touch-sensitive display and performs one or more corresponding operations in accordance with the location of the user contact.